It appears both parties don't need to be using vEmotion, only the sender needs to install it which is a grand idea as nothing is worse than having some funky new application you want to test drive and then struggling to find another user or worse still, having to persuade someone that they too should clutter up their computer with something you know little or nothing about that may or may not be a 5 minute wonder *blush* Another vEmotion perk, it appears it can be used with many of the big voice enabled IMs (Instant Messengers) like MSN Messenger, Google Talk, Yahoo! Messenger, AIM, Skype and QQ which seems a seriously cool idea as it removes the need to download yet another IM.
Personally I'm not a big "voice" user, I haven't found the need for it yet but I'm sure one day I will, until then I'll just happily plonk around with the standard graphic smileys and no background music but if you're a voice user who has used vEmotion then it would be really great to hear from you.
vEmotion homepage: http://www.voiceemotion.com